The present invention relates to devices and systems of such devices for monitoring and/or affecting parameters of a patient's body for the purpose of medical diagnosis and/or treatment. More particularly, such devices, preferably battery powered, are configured for implanting within a patient's body, each device being configured to sense a body parameter, e.g., temperature, O2 content, physical position, electrical potential, etc., and/or to affect a parameter, e.g., via nerve and/or muscle stimulation.
Commonly owned U.S. Pat. Nos. 6,164,284; 6,208,894; and 6,315,721; each entitled “System of Implantable Devices For Monitoring and/or Affecting Body Parameters” and U.S. Pat. No. 6,185,452 entitled “Battery Powered Patient Implantable Device”, each incorporated herein by reference in their entirety, describe devices configured for implantation within a patient's body, i.e., beneath a patient's skin, for performing various functions including: (1) stimulation of body tissue and/or sensing of body parameters, and (2) communicating between implanted devices and devices external to a patient's body. In an exemplary use, the implanted device is used to electrically stimulate a neural pathway and/or muscle and the same (and/or another) implanted device senses an evoked response from the intended muscle tissue and uses the detected signal to confirm that stimulation did occur and/or to achieve closed loop control. In general, the detected signal may exhibit a frequency component that corresponds to the intensity of the intended or actual muscle response and amplitude components that correspond to its proximity to the desired source tissue and/or other signal generating tissue. Depending on the application, there are various techniques that may be used to interpret the neurological signal. Such implantable devices are preferably powered using rechargeable batteries and it is desired that the time between rechargings be maximized by minimizing the power dissipation of such circuitry within these implantable devices. Accordingly, what is needed is a programmable signal analysis circuit that can be configured to interpret neurological signals using a plurality of analysis modes. Furthermore, such a circuit should minimize its power dissipation to thus enhance the battery life of the implantable devices.